Crystallization Regulation Through Monomer Sequence Control in the Carbanionic Copolymerization-Induced Crystallization Method

In this study, a strategy for regulating the crystallinity of alternating crystalline copolymers synthesized using the Carbanionic Copolymerization-Induced Crystallization (CCPIC) method was investigated in detail. First, the minimum number of repeating units for the crystallization of alternating copolymer of 9-methylene-9H-thioxanthene (MTAE) and 2,3-dimethylbuta-1,3-diene (DMBD) to produce MTAE-alt-DMBD were carefully examined using the timing sample method. The crystalline behavior was observed on more than three consecutive -MTAE-alt-DMBD- units. When the number of repeating units increased to four or more, the oligomer polymer transformed from an amorphous structure to a crystalline structure (with a crystallinity between 43 and 74%). The monomer sequence was then regulated through the addition of the third monomer 2,4-diethyl-9-methylene-9H-thioxanthene (MTAE-Et2), and consecutive -MTAE-alt-DMBD- units were broken on purpose to affect its crystalline behavior. The variations in the sequence structure of the alternating polymers were clearly confirmed by in situ 1H NMR method. Since the monomer sequence and aggregate state structure were simultaneously regulated, further development of the sequence design and the regulation of crystallinity could be attained with the living CCPIC method. By varying the feeding ratio during the living anionic terpolymerization of MTAE, MTAE-Et2 and DMBD, the terpolymers were successfully changed from amorphous to crystalline, and the crystallinity increased from 0 to 53%. And when isoprene (IP) was introduced as the highly reactive third comonomer, a gradient-alternating sequence amorphous–crystalline block polymer was successfully synthesized. This polymer exhibited polymerization-induced crystallization-driven self-assembly (PI-CDSA) behavior, forming multilamellar micelles.